Low pour point gas fuel from waxy crudes

ABSTRACT

A low pour point gas turbine fuel is prepared from a waxy crude by blending a 650*-750*F distillate fraction from a crude oil with a minor amount of a 350*-650*F fraction of a middle distillate and from 0.05 to 0.5% by weight of an oil soluble ethylene-vinyl fatty acid ester copolymer in which the fatty acid component of the ester has a carbon content of from about 2 to about 6; the copolymer having a molecular weight between about 17,000 and 29,000, and a vinyl fatty acid ester content of from about 27 to about 42. The melt index of the copolymer ranges from 7 to 465.

United States Patent Sweeney Jan. 28, 1975 LOW POUR POINT GAS FUEL FROM WAXY CRUDES lnventor: William M. Sweeney, Texaco Inc.

PO. Box 509, Bacon. NY. 12508 Filed: July 9, 1970 Appl. No.: 53,659

Related U.S. Application Data Continuation-impart ol' Ser. No. 824L358, Dec. 2, 1969, abandoned.

U.S. Cl. 44/62, 44/70 Int. Cl C10] 1/18 Field of Search 44/62, 70, 80; 252/56;

References Cited UNITED STATES PATENTS 12/1953 Wintehalter 208/15 3/l97l Aaron et al 44/62 3,640,691 2 1972 llnyckyj et a. 44/80 Primary Examiner-Daniel E. Wyman Assistant Examiner-Mrs. Y. H. Smith Attorney. Agent, or FirmT. H. Whaley; C. G. Ries {57] ABSTRACT A low pour point gas turbine fuel is prepared from a waxy crude by blending a 650750F distillate fraction from a crude oil with a minor amount of a 350650F fraction of a middle distillate and from 0.05 to 0.5% by weight of an oil soluble ethylene-vinyl fatty acid ester copolymer in which the fatty acid component of the ester has a carbon content of from about 2 to about 6; the copolymer having a molecular weight between about 17,000 and 29,000, and a vinyl fatty acid ester content of from about 27 to about 42.

The melt index of the copolymer ranges from 7 to 4 Claims, 1 Drawing Figure A/a 442m 0 +0. 25% Ava/me x +0./07, Add/me l uum Gas-017M @0001 61 -017 03.47/44: Mir/are PATENIED JAN 2 8 i975 9 ON Om LOW POUR POINT GAS FUEL FROM WAXY CRUDES This application is a continuation-in-part of Ser. No. 881,358 filed Dec. 2, 1969, now abandoned.

BACKGROUND OF THE INVENTION This invention is concerned with means for providing a turbine fuel composition at a reduced cost. More particularly, the invention is concerned with a turbine fuel composition containing a major amount of cheaper higher boiling constituents and a minor amount of more expensive middle distillate, this fuel still meeting pour point specifications owing to the incorporation therein of certain high molecular weight ethylene-vinyl fatty acid ester copolymers.

As is well known, gas oils distillates boiling at 650-750F. contain quantities of wax which render them viscous and give unacceptably high pour points. These oils behave as nonn-Newtonian liquids at low temperatures: exhibit variable solidifying temperature and peculiar hysteresis phenomena all of which render them difficult to use as fuel.

One approach used in converting these oils has been to subject them to fairly lengthy dewaxing procedures. This, however, is an expensive procedure.

Another approach which has been used to bring the viscosity of crude gas oils to suitable levels has been to dilute or cut them with a major amount of lighter distillate oils but this is an expensive procedure because of the considerably higher cost of the distillate oils relative to the higher boiling oils. Generally, the ratio of distillate to higher boiling gas oil used has been 9 to 1. The distillate can be sold directly as a diesel fuel and as such is valuable and in short supply.

A number of additives have been suggested and tried with success in lubricating oils and in so-called middle distillates in order to tie in the wax therein and improve flow at low temperatures. Such additives consist either of compounds formed by alkylating benzene or naphthalene derivatives or of copolymers of ethylenevinyl fatty acid ester of a molecular weight up to 3,000 and containing from b to 25% by weight of the vinyl fatty acid ester. These additives are not, however, effective in depressing the pour point of crude turbine fuel oils.

It is therefore the main object of the present invention to provide a fuel composition based on crude oil which will be free of the above mentioned prior art limitations.

An equally important object of this invention is to provide a turbine fuel oil composition having improved pour point characteristics by incorporating therein a minor amount of distillate oil and a small amount of certain ethylene-vinyl fatty acid ester copolymers.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The turbine fuel oil of the invention comprises from 55 to 90% by weight of crude gas oil fraction boiling at about 650-750F. and a pour point depressant additive including from 10 to 45% by weight of middle distillate oils boiling from 350 to 650 and from 0.01 to about 0.5% by weight of ethylene-vinyl fatty acid ester copolymers having a molecular weight of about 17,000 to 25,000 with a vinyl fatty acid ester (C -C content of about 24 to 42%, and a melt index of from 7 to 465.

The preferred additives contain 27 to 42% ethylenevinyl acetate copolymer having a melt index of 22 to 465 and a molecular weight ranging from about 18,000 to 21,000.

The characterization of the Elvax" copolymers is given in Table lll below. These can be added in the form of a hydrocarbon solution concentrate in, for ex ample, toluene, in the 350650F middle distillate fraction or even in the middle distillate-gas oil mixture.

The ethylene-vinyl fatty acid ester additives are then added to the gas oil and mixed with the middle distillate in an amount in the range of 0.0l% to about 0.05% by weight of the composition.

The additives may be prepared by any convenient process, such as that of US. Pat. No. 3,215,678, by a free radical-initiated polymerization of ethylene and a vinyl ester of a lower saturated monobasic aliphatic carboxylic acid. The effectiveness of the additives according to the invention is demonstrated by the following examples in which the pour points given were obtained by ASTM Method D-97-47.

EXAMPLE I There was charged to a still Mata crude oil from Guatemala which had the following characterization:

% Wax St 265dissolve in MlB hetone-cool (IF.

filter and weight wax, etc. 2.03 GravityAPI 30.06 Sulfur, Xray 0.86 Wt. Ash 0.002 Kin. Viscosity, cs at 100F. 7.52

at 150F. 3.79 Carbon residue,.wt. 3.89 Flash pt, PM,F. 58.4 Basic Nitrogen, ppm 3.93 Total Nitrogen, ppm 15 73 Pour Point,F. 15

TABLE I Y Wt. of 350- Wt. of 650- 650 P. cut 750 F. cut Kin. Vis. Pour Point (F.)

EXAMPLE II A 30% solution of Zetafax 1575 (an ethylene-vinyl acetate copolymer containing about 27% by weight of vinyl acetate and having a molecular weight of 20,000 and a Melt Index of 12-18) was prepared by dissolving by heating in toluene on a steam plate 0.1% by weight of the copolymer and incorporated in a mixture of gas oil (650-750F.) and 10% distillate (350-650F.)

and pour point, cloud point and viscosity determinations were made on the resulting mixture as well as on the pure mixture and the gas oil. The results obtained are tabulated below:

"Maximum pour point.

In the above tests, the pour point is determined by the ASTM D-97 method. The maximum pour is determined by reheating the above sample to 220F. and 4 then storing at 0F. or at a temperature below the maximum pour, whichever is lower, for at least 12 hours. The sample is then removed from cold storage, placed in a 1 15F. bath till warm and the pour point is determined. This maximum pour point determination yields a value for the pour point above which a given sample will not revert under prolonged storage or when exposed to a cyclic temperature environment.

Comparison of the data presented in Tables 1 and 11 shows immediately the advantage of the invention. It will be seen in particular that by using the additive of the invention, pour specifications can be met using 98% of the crude oil with only 10% of the more valuable 350-650F. middle distillate. On the other hand, without the additive, 95% of the middle distillate would be required with 5% of the crude gas oil (650-750F.) to achieve the desired pour point.

In other examples of the practice of the invention 0.05% of various Elvax copolymers were blended with 100% vacuum gas oil (Mata) and the pour points of each blend as well as of the additive-free oil were determined. The results thus obtained are tabulated below in Table 111. The best pour point reduction is obtained with the copolymer which has from 27-29% of vinyl acetate and a melt index of 340-470 g/l0 mm.

TABLEIII Pour Points of mixtures of various ELVAX Copolymers in 100% Vacuum Gas Oil (MATA) at 0.05% Concentration Vinyl Acetate ELVAX Pour Point.% in Copolymer Melt Index* 40 39-42 45-70 150 +45 32-34 22-28 210 +25 27-29 335-465 220 +45 27-29 125-175 240 27-29 22-28 250 27-Q9 12-18 260 27-29 5-7 310 +55 24-Q6 335-465 350 +55 24-26 16-22 360 +60 24-26 1.6-2.4 410 +55 17-19 430-580 460 l7-l9 2.1-2.9 None +65 in g/10 min. as determined by ASTM D 1328 modified.

The results obtained by the invention are graphically illustrated in the accompanying figure. 1n the figure the pour points of various blends of vacuum gas oil with middle distillates are plotted (top line). The plot of these with 0.125 and 0.1% of Elvax 210 is also given as well as that of 0.05% of the same additive in 100% vacuum gas oil.

It will be evident to those skilled in this art that the pour point depressants of this invention may be used along with other additives usually found in fuel oils of the character described. Such other additiveswill include rust inhibitors, anti-emulsifying agents, anti-static agents, anti-oxidants and the like.

1 claim:

1. A fuel oil composition having improved pour point characteristics consisting of from 55 to percent by weight of a gas oil boiling at about 650 to about 750F and an additive consisting of from 10 to 45 percent by weight of a middle distillate boiling from about 350 to about 650F, with an effective pour point depressant amount of an oil soluble ethylenevinyl fatty acid ester copolymer in which the fatty acid component of the ester has a carbon content of from about 2 to about 6. said copolymer having a molecular weight of from about 17,000 to about 29,000. a vinyl fatty acid ester content of from about 24 to about 42% and a melt index of 7 to 465.

2. A composition according to claim 1 wherein said vinyl ester is vinyl acetate.

3. A composition according to claim 1 wherein said copolymer is p esent in a concentration from about 0.01 to about 0.5% by weight of said composition.

4. The composition according to claim 1 wherein said copolymer is an ethylene-vinyl acetate copolymer having a molecular weight ranging from 18,000 to 21,000. an ethylene-vinyl acetate content ranging from about 27 to 42% and a melt index of 7 to 465. 

1. A FUEL OIL COMPOSITION HAVING IMPROVED POUR POINT CHARACTERISTICS CONSISTING OF FROM 53 TO 90 PERCENT BY WEIGHT OF A GAS OIL BOILING AT ABOUT 650= TO ABOUT 750*F AND AN ADDITIVE CONSISTING OF FROM 10 TO 45 PERCENT BY WEIGHT OF A MIDDLE DISTILLATE BOILING FROM ABOUT 350* TO ABOUT 650*F, WITH AN EFFECTIVE POUR POINT DEPRESSANT AMOUNT OF AN OIL SOLUBLE ETHYLENEVINYL FATTY ACID ESTER COPOLYMER IN WHICH THE FATTY ACID COMPONENT OF THE ESTER HAS A CARBON CONTENT OF FROM ABOUT 2 TO ABOUT 6, SAID COPOLYMER HAVING A MOLECULAR WEIGHT OF FROM ABOUT 17,000 TO ABOUT 29,000, A VINYL FATTY ACID ESTER CONTENT OF FROM ABOUT 24 TO ABOUT 42% AND A MELT INDEX OF 7 TO
 465. 2. A composition according to claim 1 wherein said vinyl ester is vinyl acetate.
 3. A composition according to claim 1 wherein said copolymer is present in a concentration from about 0.01 to about 0.5% by weight of said composition.
 4. The composition according to claim 1 wherein said copolymer is an ethylene-vinyl acetate copolymer having a molecular weight ranging from 18,000 to 21,000, an ethylene-vinyl acetate content ranging from about 27 to 42% and a melt index of 7 to
 465. 